Low nickel high-strength silicon steel

ABSTRACT

A low nickel high-strength silicon alloy steel age hardened for 8 hours at 750*F to a Vickers Brinell Hardness of 600, said alloy steel consisting essentially of C in an amount of not more than 0.03 percent, 4-6% Si, 1-5% Mn, 1.8-4.8% Ni, 6-18% Cr, 1-4% Cu, optionally one or more of Mo, V and B in an amount of not more than 2 percent each, and the residual essentially Fe, in which the weight ratio of the total amount of Ni, Mn and Cu to Si and the weight ratio of Cr to Si are varied about 2.5 and 3 respectively, wherein the Ac3 transformation point of said steel is less than 1,210*F.

llited tates v atent @ta *Uct. l, 1974 [54] LQW NICKEL HIGH-STRENGTH SILICON 3,681,058 8/1972 Dulis et a1 7 5/128 A STEEL 3,736,131 5/1973 Espy r. 75/126 B [76] Inventor: Keiichi Ota, No. 54 Shimoyamo Nakayawora-cho, Sakyo-ku, Kyoto, Japan Notice: The portion of the term of this patent subsequent to July 4, 1989, has been disclaimed.

[22] Filed: Apr. 16, 1973 [21] Appl. No.: 351,169

[52] U.S. C1. 148/37, 75/125, 75/126 B, 4 75/126 Q, 75/128 A, 75/128 C [51] Int. Cl. C22c 39/20, C220 39/44 [58] Field of Search 148/37; 75/125, 126 B, 75/126 Q, 128 A, 128 C [56] References Cited UNITED STATES PATENTS 1,892,384 12/1932 Cox et a1. 75/126 Q 2,789,049 4/1957 De Long et a1. 75/126 B 3,674,468 7/1972 Ota 75/125 X OTHER PUBLICATIONS Steel and Its Heat Treatment, Vol. III, Bullens, 1949, p. 26.

Primary ExaminerL. Dewayne Rutledge Assistant ExaminerArthur J. Steiner [5 7 ABSTRACT A low nickel high-strength silicon alloy steel age hardened for 8 hours at 750F to a Vickers Brinell Hardness of 600, said alloy steel consisting essentially of C in an amount of not more than 0.03 percent, 4-6% Si, 15% Mn, 1.84.8% Ni, 618% Cr, l4% Cu, optionally one or more of Mo, V and B in an amount of not more than 2 percent each, and the residual essentially Fe, in which the weight ratio of the total amount of Ni, Mn and Cu to Si and the weight ratio of Cr to Si are varied about 2.5 and 3 respectively, wherein the A03 transformation point of said steel is less than 1,210F.

1 Claim, No Drawings SUMMARY AND PREFERRED DISCRlPTlON OF 35 LOW NICKEL HIGH-STRENGTH SILICON STEEL cent and by controlling the total amount of the essential elements Ni, Mn and Cu to be 2.5 times the Si con- BACKGROUND. OF THE INVENTlON v tent whereby the Ac3 transformation point surprisingly The present invention is related to an improvemen k will be less than 1,210F notwithstanding the reduction over my High-strength Silicon Steel disclosed and 5 of the amount of nickel in the alloy. These surprising claimed in my U.S. Pat. No. 3,674,468 granted on July results are attributed to the inclusion in the alloy of 4, 1972. 7 y from 1 to 4 percent copper with the proviso that the My U.S. patent relates to an invention of highamount of copper together with nickel and manganese strength silicon steel consisting essentially of: be 2.5 times the silicon content.

H--- T B 2-. a

Kind of Steel Mark Chemical Composition! 7( I Ac3 Transforma- C Si Mn Ni Cr Mo+V Cu tion Point (F) Low Ni High-strength Si Steel according A 0.016 4.08 4.85 3.36 12.86 1.05 1.96 1260 to Present Invention 0.022 4.83 4.12 4.08 11.75 0.68 3.22 1210 High-strength Si Steel Pat. 3674468 0.018 4.58 2.75 6.63 10.48 2.21 0.18 1160 NiCrMo Steel 4337 0.274 0.23 0.65 3.13 1.16 0.32 0.22 1440 ingredient weigiifpe'rfit T51511 ."1 i'n dl c'ates Ehrriic'lil 'asnissatianaaa'iraa for- C Up to m mation point of steel according to the present invention Si 25 comparing with those of the patented steel 3,674,468 N1 I -10 I and NiCrMo steel 4337.

Cr 6-18 and about 2.5 times Si content T bl 2 h t Mn MO and Cu up to 4 respectively a e s ows the mechanical properties of steels m tip to 2" h I d Table 1 at various conditions and it Wlll be appreciated e I. i l Ni Mn 28221 that the Quality Factors of the low nickel high-strength silicon steels according to the invention are slightly V I V W lower than those ofthe above-mentioned high-strength Wh r the tfansfol'manon poll of Sald Steel silicon steel in the solution-treated state but they are less than 1,210 F. much higher than those of the heat-treated NiCrMo steel 4337.

To give high strength-and-toughness, plentiful forge- THE [NVENTON ability and corrosion resistance to a two-phase alloy The present invention relates to a low nickel highconsisting of Ferrite and Austenite, it is necessary to strength silicon steel which can be produced more ecohave a suitable structure of about 40-50 percent Fernomically than the above mentioned high-strength silirite to Austenite at the solution treated state as decon steel by lowering the Ni content to less than 5 per- 40 scribed in the following Table 3.

" """Tzible 2 Kind of Steel Mark Heat-treatment Mechanical Properties Quality Factors T.S. Elong R.A. T.S.X T.S.X v lb/sq.in 7: "/2 Elong. R.A.

Low Ni High-strength A 1920 1 hr W.Q. 150,000 75 6750000 11250000 Si Steel according 1920X1 hr A.C.. 140,000 40 5600000 7700000 to Present Invention B l830 l hr W.Q. 158.000 42 6640000 11060000 1830X1 hr A.C. 145,000 38 58 5510000 8410000 High-strength Si 1650X1 hr W.Q. 165,000 48 74 7900000 12000000 Steel Pat. 3674468 1650X1 hr A.C. 150,000 52 68 7800000 10200000 1560 l hr 0.0. NiCrMo Steel 4337 1200Xl hr 0.0. 160.000 25 61 4000000 9800000 Tab Content 01' Alloying Element Ac3 point Structure Characteristics of Allov in 7! in C Ratio of Forge- T.S. 1.V. Corrosion Ni Mn Cu Si Fto A ability Resistance 5 0 Ni+Mn=2 Si 500-650 Z/S-k Good High Good Fairly 5 Ni+Mn+Cu 2.5 Si 650 /2 Poor Too High Poor Poor 5 Ni+Mn+Cu=2.5 Si 500-650 2/5-V2 Good High Fairly Good 5 Ni+Mn+Cu 2.5 Si 500 2/5 Good Low Good Better N.B. F: Ferrite, A: Austenite **T.S.: Tensile Strength, 1.V.: Impact Value. Corrosion Resistance: For H 50 500-650C=900-1200F ered almost to full Austenite alloy such as AlSl 31'6L,

and on the contrary, the' Ac3 point above 650C, the

gforgeability and corrosion resistance are fatally droped. This is the reason that the total amount of the Ni, Mn

and Cu to the Si and the Cr to the Si are determined to 2.5 and 3 respectively.

' ra'z'afiiseasaiama tial; actionof" iawerrig A53 transformation point by alloying Cu compared with Ni, the ratio of the total amount of Ni, Mn and Cu to the Si content is increased 0.5 percent than Pat. No. 3,674,468,

new nickel higrliaragmmaaa Steel accaraag that of US.

to the invention has a peculiar characteristic on aging and can harden so high hardness as Vickers Brinell Hardness of 600 by aging for 8 hours at 750F after cold-rolled to /2 inch thickness from five-eighths inch, without practically any loss of ductility and corrosionresistance as described in the following Table 4.

facture of a piano-wire having tensile strength of 205,0- lb/sq.in. and plentiful toughness by applying strainaging at 750F.

c. It has a very high toughness of more than 5 kg.m/sq.cm of Charpy lmpact Value in as-cast cohdition and suitably used for high-strength steel castings such as marine propeller high-strength steel castings.

The present invention may be applied to the manufacture of a wide variety of ferrous products and articles which will be apparent to those skilled in the metallurgyofsteel from he properties of this steel provided by ,the inventi ofi.' These products and particles include machine parts such as reaction vessel for chem- 'ical industry, turbine-disc of jet engine, chassis of cars, plates for shipbuilding, corrosion-resisting high-tension wire-rope and PWS for suspension bridge and oceandevelopment, many kinds of springs and various IUSt-g USES.

Table 4 Condition Mechanical Properties Corrosion Loss Hardness T.S'. Elong RA. 5% H 80 5% HCl 5%HNO HV lb/sq. in 7c 7r gr/m /gr l/h z As Cold-rolled to /2 in.thickness 480 228,000 28 6 80 0.3 from in. As Solution-treated after Cold-rolled 300 135.000 55 80 I 4 60 0.2 As Aged for 8 hours at 780F 630 205,000 33 I 55 5 130 0.3

itiadaiiiofi to the foregoing mechanical ant corrosion-resisting properties, it has been confirmed that the low nickel high-strength silicon steel according to the invention has the following excellent characteristics and properties:

a. It is rich in castability and well adapted for precision casting of thin and complex-formed machine parts such as turbine blades.

b. It has an ample forgeability and permits the manu- 

1. A LOW NICKEL HIGH-STRENGTH SILICON ALLOY STEEL AGEN HARDENED FOR 8 HOURS AT 750*F. TO A VICHERS BRINELL HARDNESS OF 600, SAID ALLOY STEEL CONSISTING ESSENTIALLY OF C IN AN AMOUNT OF NOT MORE THAN 0.03 PERCENT, 4-6%SI, 1-5% MN, 1.8-4.8% NI, 6-18%CR, 1-4% CU, OPTIONALLY ONE OR MORE OF MO, V AND B IN AN AMOUNT OF NOT MORE THAN 2 PERCENT EACH, AND THE RESIDUAL ESSENTIALLY FE, IN WHICH THE WEIGHT RATIO OF THE TOTAL AMLOUNT OF NI, MN AND CU TO SI AND THE WEIGHT RATIO OF CR TO SI ARE VARIED 2.5 AND 3 RESPECTIVELY, AND WHEREIN THE AC3 TRANSFORMATION POINT OF SAID STEEL IS LESS THAN 1,400*F. 